Nothing about the premise of “Pitch Perfect” suggests it should be a funny movie, or anything more than a diversion for “Glee” fans who’ve burnt out on the hit show after three-plus seasons. A cappella groups might be a change of pace for Hollywood, but college humor isn’t, with most college comedies going straight to DVD bargain bins these days.

So even after seeing “Pitch Perfect,” it’s a total wonder how it manages to stay fresh and entertaining. College movie clichés lurk around every possible turn of the plot, but “30 Rock” writer and producer Kay Cannon, who essentially wrote the movie (it resembles Mickey Rapkin’s book in name only), artfully dodges, embraces and twists them in surprising ways, and the cast working with it fulfills its end of the bargain too.

The film stars Anna Kendrick as Beca, a freshman at fictional Barden University who’s an aspiring DJ preoccupied with mixing her own mashups. Reluctantly, she’s recruited by the Bellas, the school’s all-female vocal ensemble, led by the authoritarian Aubrey (Anna Camp), who’s hell-bent on taking the International Championship of Collegiate A Cappella (which exists, actually) away from the school’s all-male group, the Treblemakers. Problem is, Aubrey wouldn’t know hip if it bit her in the ass. Beca rolls with their old-school ways and never- ending performances of Ace of Bass’ “The Sign” until it’s clear they need a shakeup if they want to win it all.

But “Pitch Perfect” isn’t some competitive singing movie that plays out as a “will they or wont’ they win?” drama. In fact, there’s almost a total disregard for that element of the story. Audiences who go primarily for the music might even be a tad disappointed that most of the songs are kept to snippets, and director Jason Moore does little to emphasize the quality of the singing or the music itself. The script sticks squarely to comedy, hoping to surprise you with its sense of humor.

The best comedies have strong supporting characters who can take attention away from the predictable core story, usually a romance, in this case Beca’s friendship and eventual spurning of Jesse (Skylar Astin), a freshman Treblemaker who interns with Beca at the campus radio station. “Pitch Perfect’s” ace is Aussie Rebel Wilson, the recognizable roommate from “Bridesmaids,” who plays Fat Amy, a new Bella with boisterous personality and loads of confidence. Wilson’s one-two punch of deadpan and self-deprecating humor takes the edge off the “Mean Girls” dynamic established between Beca and the two older Bellas, Aubrey and Chloe (Brittany Snow).

The other girls in the group possess just the right amount of quirkiness to be memorable rather than stereotypical. There’s a black lesbian, a whispering Asian and a tall slut to name a few. The guys of the Treblemakers, led by Bumper (Adam DeVine of “Workaholics”), act cool, but in the nerdiest way possible. The script is keen on reminding us that these characters are all in singing groups, and therefore by definition, nerdy.

The laughs extend as far as the competition commentators, played John Michael Higgins and Elizabeth Banks, who frankly don’t exist. No one is listening on the radio to these things, and it’s not even clear they’re even being broadcasted. But they’re for our enjoyment to be sure. Not since the team of Gary Cole and Jason Bateman in “Dodgeball” have commentators been this funny.

“Pitch Perfect” thrives on this genuine wit, which perfectly masks how irrelevant the rest of the movie is. As the director of hit Broadway show “Avenue Q,” Moore understands how humor and music work, but even he would concede “Pitch Perfect” is about the former. The script’s sharpness is matched only by it’s conscious effort to avoid the clichés that comes with this territory. Even if you think you know what the joke is going to be, there’s some twist that will come later.

The ending, always the worst parts of these movies, avoids all the gooey stuff too. It’s so nice to see a conscious effort to deliver something unexpected in a genre that filmmakers so often use as an excuse to lean on the conventional. It just so happens that a movie about college a cappella was lucky enough to be the recipient of this refreshing approach.